The United States said Monday that it would suspend some economic sanctions on Iran after it slowed its nuclear program, but officials are still scrambling to block a United Nations invitation for Iran to join upcoming Syria peace talks.

The mixed messages reflect the conflicting priorities that currently define U.S.-Iran relations: a breakthrough in negotiations over Iran’s nuclear ambitions and deadlock over the country’s support for the regime of President Bashar Assad in Syria’s nearly-three-year civil war.

The White House said Monday that the U.S. will begin easing sanctions after the UN’s International Atomic Energy Agency reported earlier that Iran had taken initial steps—including ending production of 20-percent enriched uranium—to comply with the internationally-brokered interim agreement reached in November. The European Union made a similar announcement earlier Monday.

“These actions represent the first time in nearly a decade that Iran has verifiably enacted measures to halt progress on its nuclear program, and roll it back in key respects,” the White House said in a statement. “In reciprocation for Iran’s concrete actions, the United States and its P5+1 partners—the United Kingdom, France, Germany, Russia, and China, as well as the European Union—will today follow through on our commitment to begin to provide the modest relief agreed to with Iran.”

The statement said the U.S. will continue to enforce remaining sanctions during the six-month period slated for negotiations toward a permanent deal. The Treasury Department published guidelines on the suspended sanctions to its website in conjunction with the announcement.

But U.S. officials are reportedly demanding that the U.N. withdraw an invitation, which Secretary-General Ban Ki-moon unexpectedly extended to Iran Sunday, to join peace talks on Syria this week in Switzerland.

Citing unnamed senior U.S. officials, the Associated Press reports that U.S. wants the invitation dropped unless Iran publicly endorses the creation of a transitional government in Syria that is the underlying goal of this week’s talks. Ban told the Security Council that “intensive and urgent” discussions are underway and he will say more later in the day.